Chemistry Honor

Science & Health

Requirements

  1. Define the following:
    • Compound
    • Solutions
    • Chemical Transformation
    • Physical Transformation
    • Atoms
    • Proton
    • Neutron
    • Electrons
    • Molecules
    • Acid
    • Salt
    • Distillation
    • Fractional distillation
    • Filtration
    • Combustion
    • Fractional dissolution
    • Acid/Base indicators

    Answer: 1) Compound: a substance formed by two or more different chemical elements joined in a fixed proportion by chemical bonds (e.g., water, H2O). 2) Solutions: a homogeneous mixture of two or more substances, formed by a solute dissolved in a solvent (e.g., salt dissolved in water). 3) Chemical Transformation: a change in which the original substance turns into one or more different substances, with a new composition (e.g., burning wood, rusting iron). 4) Physical Transformation: a change that alters only the shape, size, or physical state, without changing the substance (e.g., melting ice, crumpling paper). 5) Atoms: the smallest unit of matter that retains the properties of a chemical element; it is made up of a nucleus and an electrosphere. 6) Proton: a positively charged particle located in the nucleus of the atom; the number of protons defines the element. 7) Neutron: an uncharged (neutral) particle located in the nucleus of the atom, along with the protons. 8) Electrons: negatively charged particles that orbit around the nucleus, in the electrosphere. 9) Molecules: a grouping of two or more atoms joined by bonds, forming the smallest part of a substance that retains its properties (e.g., O2, H2O). 10) Acid: a substance that, in solution, releases H+ (hydrogen) ions, has a sour taste, and turns the indicator red (e.g., vinegar, lemon). 11) Salt: a substance resulting from the reaction between an acid and a base (neutralization), such as table salt (NaCl). 12) Distillation: a separation process that heats a liquid mixture until it boils, collecting and cooling the vapor to recover the pure liquid. 13) Fractional distillation: distillation that separates liquids with different boiling points within the same mixture, collecting each one at its temperature (e.g., separating the components of petroleum). 14) Filtration: the separation of an insoluble solid from a liquid (or gas) by passing the mixture through a filter that retains the solid. 15) Combustion: a rapid chemical reaction of a substance with oxygen, releasing heat and light (burning). 16) Fractional dissolution: the separation of a mixture of solids using a liquid that dissolves only one of them, separating it from the other by filtration. 17) Acid/Base Indicators: substances that change color depending on whether the medium is acidic or basic, indicating the pH (e.g., litmus paper, phenolphthalein, red cabbage juice). — These terms are the basis of high school chemistry. Acids have pH < 7, bases > 7, neutral = 7. Indicators like phenolphthalein change color at a specific pH. Exothermic combustion releases heat. The proton has a charge of +1, the electron −1, and the neutron is neutral - they are the three basic subatomic particles.

  2. Find out:
    • What is the periodic table and what is its importance?
    • What are chemical elements?
    • How are the elements grouped in the table?
    • What is atomic number?
    • How are the elements represented in the table?

    Answer: Research and describe: 1) The Periodic Table organizes the 118 known chemical elements by increasing atomic number (the quantity of protons in the nucleus), into periods (horizontal rows) and groups/families (vertical columns with similar properties). It was systematized by Dmitri Mendeleev in 1869. 2) A chemical element is a pure substance formed by a single type of atom (the same atomic number), such as hydrogen, oxygen, iron, and gold; it is represented by a symbol (H, O, Fe, Au) and cannot be broken down into simpler substances by ordinary chemical means. — The table was created by Mendeleev in 1869, before many elements were discovered - he predicted the properties of missing elements that were later confirmed. Today the IUPAC recognizes 118 elements. Each element has a unique symbol, an atomic number (Z), and an average atomic mass.

  3. Which gases eliminate life? How? Explain the principle of a chemical compound that extinguishes fire.

    Answer: Lethal gases: carbon monoxide (CO, prevents oxygenation of the blood), carbon dioxide in high concentration (asphyxiation), cyanide and chlorine (toxic inhalation). To extinguish fire: CO₂ or chemical powder (NaHCO₃) - they remove oxygen and/or interrupt the chemical reaction, smothering the flame. — CO binds to hemoglobin 200x more than O₂, causing hypoxia. The 'fire tetrahedron' needs 4 elements: fuel, oxygen, heat, and chemical reaction. ABC extinguishers remove one or more. CO₂ is effective because it is denser than air, displacing oxygen from around the seat of the fire.

  4. Mention 2 common sources of carbon monoxide. Why is it a dangerous substance?

    Answer: Two sources: 1) car and motorcycle exhaust; 2) incomplete combustion of gas stoves/heaters or fireplaces with poor ventilation. CO is dangerous because it is colorless, odorless, and binds to hemoglobin 200x more than O₂, preventing oxygen transport and causing a silent, fatal poisoning. — About 50,000 Brazilians go to hospitals for CO poisoning each year, according to the Ministry of Health. Because it has no smell or color, victims fall asleep and do not notice. Initial symptoms: headache and dizziness. Prevention: adequate ventilation, equipment maintenance, and CO detectors in the home.

  5. What are the physical states of matter?

    Answer: The classic physical states are: 1) Solid (defined shape and volume), 2) Liquid (defined volume, shape of the container), 3) Gaseous (no defined shape or volume). — Plasma is the most abundant state in the universe (99% of visible matter). The transition between states involves latent heat - heat that changes the state without altering the temperature. There is also the Bose-Einstein condensate (5th), created in the laboratory at temperatures near absolute zero.

  6. Choose, explain the phenomenon involved, and do 5 of the following alternatives:
    • Try to light a sugar cube, first without and then with some ashes applied to the cube, demonstrating the catalytic action.
    • Place an ice cube in a glass of water, lay a 10-centimeter string on top of the ice in the glass, then solve the problem of removing the ice cube from the water without touching it.
    • Using water, white spirit, and soap, transfer a newspaper photo onto a blank sheet of paper.
    • Using a basin of water, wooden matches, a lump of sugar, and a little soap, demonstrate the action of sugar and soap on matches floating in the water.
    • Place a fresh egg in fresh water and then salt it, noting the difference.
    • Demonstrate the colors produced when the following elements are burned: salt, copper, sulfate, and acid.
    • Make an invisible ink
    • Using 3 pieces of candle of different sizes and a glass container, explain convection currents and gas density.
    • Using a candle, a piece of paper, and a glass screen, explain incomplete combustion through the compound formed. How many and which phenomena are involved when a candle is lit?
    • Demonstrate the thermal capacity of water using some of the following materials: a candle, a balloon, water, 20% alcohol, acetone, paper, a wire tripod, pleated paper.
    • Using magnesium shavings, a candle, and an acid/base indicator, indicate the type of reaction involved and demonstrate the acidity or basicity of the compound formed.
    • Using 2 glass tubes, 2 wooden skewers, sodium bicarbonate, vinegar, potassium iodide, and hydrogen peroxide, demonstrate combustion in the presence and in the absence of oxygen.
    • Using some acid/base indicators, demonstrate the acidity or basicity of some products found in our daily lives. Also demonstrate a reversible reaction.
    • At a campsite, through carelessness, a Pathfinder spilled the sugar that was supposed to be used to sweeten the meal's juice into the sand. Using what is available at the campsite, propose the steps of a method to separate the components of the mixture in question. Then, state whether any chemical or physical transformation occurred.
    • How many and which phenomena are involved when a candle is lit?

    Answer: Choose 5 experiments from the list, perform them in a safe laboratory with supervision, and explain the chemical/physical phenomenon in each one. Document with photos and a report describing the theory behind it. — Invisible ink made with lemon juice becomes visible with heat (it caramelizes). Salt burns yellow (sodium); copper burns green. An egg floats in salt water because of its higher density. Each experiment illustrates a specific concept: catalysis, density, combustion, convection. Safety (gloves, goggles) always.